Add a KeysInterface to bridge between user wallet and others lightning

componenets, responsible to get seed from the former and derive
appropriate keyring materials

Author: Antoine Riard

src/ln/keysinterface.rs

@@ -6,6 +6,11 @@
 //! appropriate keyring materials to others lightning components, as such node_id, destination_script.
 //!
 
+
+use bitcoin::blockdata::script::Script;
+
+use secp256k1::key::SecretKey;
+
 use ln::msgs;
 
 /// A trait to describe a wallet which sould receive data to be able to spend onchain outputs
@@ -18,3 +23,15 @@ pub trait WalletInterface: Send + Sync {
 	/// BOTL 3 derivation scheme.
 	fn handle_spendable_output(&self, msg: &msgs::SpendableOutputs);
 }
+
+/// A trait to describe an object which should get secrets from user wallet and apply derivation
+/// to provide keys materials downstream
+pub trait KeysInterface: Send + Sync {
+	/// User wallet has to provide this KeysInterface with a master seed used to derive 
+	/// node_id as /0' and destination_script as /N'
+	fn provide_master_seed(&self, seed : [u8; 32]);
+	/// Get node secret key to derive node_id
+	fn get_node_secret(&self) -> Option<SecretKey>;
+	/// Get destination script to encumber protocol exit points
+	fn get_destination_script(&self) -> Option<Script>;
+}